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"Basal Eurasian" may be ~80 ky old
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[QUOTE]Originally posted by Tyrannohotep: [QB] [URL=https://www.biorxiv.org/content/early/2018/03/23/287268]Efficiently inferring the demographic history of many populations with allele count data[/URL] From the abstract: [QUOTE]The sample frequency spectrum (SFS), or histogram of allele counts, is an important summary statistic in evolutionary biology, and is often used to infer the history of population size changes, migrations, and other demographic events affecting a set of populations. The expected multipopulation SFS under a given demographic model can be efficiently computed when the populations in the model are related by a tree, scaling to hundreds of populations. Admixture, back-migration, and introgression are common natural processes that violate the assumption of a tree-like population history, however, and until now the expected SFS could be computed for only a handful of populations when the demographic history is not a tree. In this article, we present a new method for efficiently computing the expected SFS and linear functionals of it, for demographies described by general directed acyclic graphs. This method can scale to more populations than previously possible for complex demographic histories including admixture. We apply our method to an 8-population SFS to estimate the timing and strength of a proposed "basal Eurasian" admixture event in human history. We implement and release our method in a new open-source software package momi2.[/QUOTE]And from the preprint's text: [QUOTE]Our inferred demography, along with nonparametric bootstrap re-estimates, are shown in Figure 2 and Table 2. Our parametric bootstrap estimates are shown in Figure 3. We inferred a pulse of 0.094 (95% CI of 0.049-0.174) from the ghost Basal Eurasian population to EEF ancestry (LBK), substantially less than the 0.44 inferred by (Lazaridis et al., 2014). This admixture was inferred to occur 33.7 kya (95% CI of 10.8-41.1 kya), shortly after the Loschbour-LBK split at 37.7 kya (95% CI of 32.2-42.3 kya). [qb]The split time of the ghost Basal Eurasian lineage from other Eurasians was inferred at 79.8 kya (95% CI of 67.4-101 kya).[/qb] Other parameters were broadly in line with previous estimates, such as a Mbuti-Eurasian split of 96 kya, a Han-European split of 50 kya, a Neanderthal split of 696 kya, and Eurasians deriving 0.03 of their ancestry from Neanderthal (Terhorst et al., 2017; Green et al., 2010; Meyer et al., 2016).[/QUOTE]If memory serves, the big OOA event took place between 70-50 kya. So Basal Eurasian emerging as a distinct component ~80 kya would make it older than OOA itself. The implications of this should be obvious by now. ;) [/QB][/QUOTE]
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